(sociology) a hypothetical mode of society, made up of self-serving individuals linked by impersonal ties; as opposed to Gemeinschaft

1973, Thomas Pynchon, Gravity's Rainbow:

Seven years later, Hernández wrote a Return of Martín Fierro in which the Gaucho sells out: assimilates back into Christian society, gives up his freedom for the kind of constitutional Gesellschaft being pushed in those days by Buenos Aires.